Research And Application Of Gold Nanoparticles On Detection Of Nucleic Acid

Quartz crystal microbalance (QCM) is known to provide very sensitive mass-measuring devices in gas phase and in aqueous solution Free of using specific indicators, the QCM is a promising candidate for the detection of DNA hybridization. Au nanoparticles have been shown to be biocompatible, large areas, all these make them potential for enhancing the sensitivity of DNA detection . Au nanoparticles have been introduced to modify QCM gold chip in this paper. The gold nanoparticles with anaverage diameter of 5nm,15nm,25nm were prepared by reduction of HAuCl4 with sodium citrate aqueous solution.1,6-Hexanedithiol was used as the medium to attach Au nanoparticles on the gold chip. DNA probe with a mercaptohexyl group at the 5'end was assembled onto gold chip modified with three kind of gold nanoparticles, and then hybridized with complementary DNA. QCM was employed to investigate the experimental process.We described herein initial studies on the assembly of 1,6-Hexanedithiol, different size of gold nanoparticles, DNA probe and its hybridization. We studied emphatically the kinetics of assembly and hybridization of DNA probes onto the gold chip modified with gold nanoparticles . We show that covalent attachment of Au nanoparticles leads to an increased capacity for DNA assembly and hybridization than those in the absence of the gold particles. This enhancement effect was dependent on the size of the gold nanoparticle, in particular, lower surface density and higher hybridization efficiency were obtained with 25nm gold nanoparticle compared to 5 nm and 15 nm gold nanoparticles. With an improved ability for immobilization of DNA probe, the new method has been potential to enhance sensitivity to the target DNA in solution, by hybridizing a greater amount at a given concentration. The kinetics of Au nanoparticles self-assembled on dithiol-modified gold chip was investigated. During the formation of Au nanoparticles films on the Au substrate, QCM was used to monitor the progress of the surface reaction of Au nanoparticles with dithiol. It was found that the rate of formation of the first monolayer with relatively smaller particles is faster than larger particles, whereas for larger particles the multilayer formation rate is much faster than smaller particles.Although a bimolecular reaction model adequately described solution-phase hybridization kinetics, however, according to experimental data , DNA hybridization on gold nanoparticles did not fit this model but exhibited biphasicreaction kinetics. Rate constants for hybridizations on the particle surface were about an order of magnitude less than those for hybridization in solution, but decreasing the surface density of DNA probe improved hybridization rates. Finally, the thesis discussed the application foreground of gold nanoparticles in the field of piezoelectric detection DNA. In a word, this work suggests a prominent role for gold nanopartices in the development of nucleic acid sensors.